With the development of wireless communication technology, users demand new services having high quality and high speed. Wireless communication operators and device manufacturers need to continuously improve systems to meet the demands of the users. In this case, a large amount of frequency spectrum resources are required to support the new services and meet requirements of high speed communications. The frequency spectrum resources may be quantized by parameters such as time, frequency, band width, maximum allowable transmission power. Currently, limited frequency spectrum resources have been allocated to fixed operators and services, a new available frequency spectrum is very rare or expensive. In this case, a concept of dynamic frequency spectrum usage is proposed, in which frequency resources that have been allocated to certain services but are not utilized sufficiently are utilized dynamically.
As an intelligent evolution of software radio technology, the cognitive radio (CR) technology enables an unlicensed user to dynamically access a licensed frequency spectrum according to certain rules, which greatly improves actual frequency spectrum utilization efficiency. It may be considered that a cognitive radio system includes a primary system and a secondary system, where a system that is licensed to use the frequency spectrum serves as the primary system, and an unlicensed communication system that can dynamically access the licensed frequency spectrum according to certain rules serves as the secondary system. Alternatively, the secondary system may also be a system having a frequency spectrum usage right but having a lower frequency spectrum utilization priority than the primary system. In addition, a functional module called as a spectrum coordinator (SC) and a functional module called as a geographic location database (DB) may further be arranged in a region to manage the secondary system and distribute a resource for the secondary system.
The communication mode in which the primary system and the secondary system coexist requires that the secondary system does not adversely affect the primary system, or the impact generated by the secondary system is controlled within the tolerance of the primary system. In a case that there are multiple secondary systems, aggregation interference generated by the secondary systems cannot exceed the interference tolerance range of the primary system. Therefore, it is desired to propose a mechanism for frequency spectrum distribution, so that the frequency spectrum distribution for the secondary system is more reasonable so as to improve the frequency spectrum utilization efficiency.